Photoinduced Charge Shifts and Electron Transfer in Viologen–Tetraphenylborate Complexes: Push–Pull Character of the Exciplex

• DOI: 10.1021/jacs.7b01946
• Publication Date: 2017-05-16T14:34:50Z
• Authors: Willy G. Santos; Darya S. Budkina; Victor M. Deflon; Alexander N. Tarn...; Daniel R. Cardoso; Malcolm D. E. Forbes
• Keywords: Tetraphenylborate; Viologen; Excimer; Photoinduced electron transfer

Viologen-tetraarylborate ion-pair complexes were prepared and investigated by steady-state time-resolved spectroscopic techniques such as fluorescence femtosecond transient absorption. The results highlight a charge transfer transition that leads to changes in the viologen structure excited singlet state. Femtosecond absorption reveals formation of excited-state stimulated emission bands assigned planar (kobs < 1012 s-1) twisted ∼ 1010 structures between two pyridinium groups ion. An efficient photoinduced electron from tetraphenylborate anionic moiety dication was observed less than 1 μs after excitation. This is consequence push-pull character donor structure, which helps borate triplet state deactivated further via second process, generating cation radical (V•+).